Mass spectroscopy is just one of several analytical techniques which require ion or charged particle detectors. Other applications in which ion or charged particle detection is required include electron energy analyzers, electron capture detectors, flame ionization detectors, photoionization detectors, ion mobility spectrometers, smoke and particle detectors or any application in which ions in solutions are collected and measured. Typically in applications which require an array it is necessary to use a costly and complex micro channel plate, phosphor-fiber optic-photodiode array assembly to detect ions directly. In single channel applications it is possible to detect ions directly with a multiplier device such as an electron multiplier, a channel electron multiplier (CEM) or a discrete dynode electron multiplier. It is also possible to use a phosphor to convert ions to photons, and then detect them with a photomultiplier. A Faraday cup collector and an electometer may also be used.
Replacement of channel electron multipliers or other detectors in, for example, quadrupole mass spectroscopy and in other applications would be of value in providing cost savings and improved performance. Preferably a detector should be insensitive to vacuum quality and should not be adversely affected by exposure to atmosphere. Further, if at all possible, it should not require high voltages, should not exhibit mass discrimination, and should not respond to neutral particles or low energy photons.
U.S. Pat. No. 5,386,115 to Freidhoff et al. discloses a solid state mass spectrograph which includes an inlet, a gas ionizer, a mass filter and a detector array all formed within a cavity in a semiconductor substrate. The detector array is a linear array oriented in the dispersion plane of the mass filter and includes converging electrodes at the end of the cavity serving as Faraday cages which pass charge to signal generators such as charge coupled devices formed in the substrate but removed from the cavity.